n = int(input())
s = input()

num_r = s.count("R")
count = 0

for i in range(num_r):
    if s[i] != "R":
        count += 1
    
print(count) n = int(input()) n int(input()) int input() input s = input() s input() input num_r = s.count("R") num_r s.count("R") s.count s count "R" count = 0 count 0 for i in range(num_r):
    if s[i] != "R":
        count += 1
     i range(num_r) range num_r if s[i] != "R":
        count += 1
     s[i] != "R" s[i] s i "R" count += 1 count 1 print(count) print count num_r = s.count("R") s.count("R") num_r s = input() input() s n = int(input()) int(input()) n count = 0 0 count count += 1 1 count
n = int(input())
s = input()

num_r = s.count("R")
count = 0

for i in range(num_r):
    if s[i] != "R":
        count += 1
    
print(count)